1. Technical Field
The present invention relates to a mounting structure, an electro-optical device, an electronic apparatus, and a method of producing the mounting structure. More particularly, the invention relates to a structure of a protruding electrode provided at an electronic component.
2. Related Art
In general, various electronic components, such as semiconductor devices, including a protruding electrode (bump electrode), provided on a surface of a substrate so as to protrude therefrom, are known. The protruding electrode is adhered to, for example, a substrate, at a side where mounting is performed, for electrical conduction. In general, a metallic bump electrode, formed by, for example, thickly plating a seed electrode with a metal (such as Au), is used as the protruding electrode. For example, a method of mounting a driving IC on a substrate of various display members is known as a mounting method using such a protruding electrode.
A proposal of using, as the above-described protruding electrode, a protruding electrode formed by forming a resinous protruding member on a substrate and forming an electrically conductive layer on a surface of the protruding member has been proposed (refer to, for example, JP-A-2005-136402 and JP-A-2005-101527 below). Compared to a related metallic bump electrode, this type of protruding electrode can use a thinner electrically conductive layer, so that fine patterning can be performed, thereby making it possible to reduce an electrode pitch. In addition, the use of a resinous protruding member makes it possible to ensure a stable contact pressure as a result of making use of elastic deformation of the protruding member, so that, compared to a related bump electrode, electrical reliability can be increased, etc.
A top portion of the protruding electrode discussed in each of JP-A-2005-136402 and JP-A-2005-101527 is squashed by a facing electrode during mounting. When a deformation amount of the protruding electrode is too large, for example, a crack occurs in the aforementioned resinous protruding member or the electrically conductive layer, formed on the protruding member. This results in variations in electrical conductivity of the protruding electrode and an increase in a resistance value, thereby reducing electrical reliability.
That is, in general, mounting is performed as a result of setting a compression force at the time of mounting in a range in which the protruding electrode does not crack. Since variations exist in, for example, the form of the protruding electrode, the elastic modulus of a constituent material, the mounting temperature, and the compression distribution, even if the mounting is performed under the previously set compression force, variations occur in the amount of deformation of the protruding electrode. Therefore, it is not possible to eliminate the possibility of, for example, the protruding electrode becoming cracked (as well as deformation of the electrically conductive layer resulting from variations and an increase in resistance. This also applies to the discussion below). To sufficiently reduce this possibility, it is necessary to set the compression force considerably lower than a limit value. However, when this is done, contact pressure or contact area may no longer be ensured due to an insufficient deformation amount of the protruding electrode. Therefore, in either case, variations or an increase in a conductive connection resistance occurs, thereby resulting in improper mounting in extreme cases.